/* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.

 * Copyright (c) 2007-2021, The Tor Project, Inc. */

/* See LICENSE for licensing information */

/**

 * \file rendmid.c

 * \brief Implement introductions points and rendezvous points.

 **/

#include "core/or/or.h"

#include "core/or/channel.h"

#include "core/or/circuitlist.h"

#include "core/or/circuituse.h"

#include "app/config/config.h"

#include "lib/crypt_ops/crypto_cipher.h"

#include "core/or/dos.h"

#include "core/or/relay.h"

#include "feature/rend/rendmid.h"

#include "feature/hs/hs_circuitmap.h"

#include "feature/hs/hs_dos.h"

#include "feature/hs/hs_intropoint.h"

#include "feature/relay/relay_metrics.h"

#include "core/or/or_circuit_st.h"

/** Process an ESTABLISH_RENDEZVOUS cell by setting the circuit's purpose and

 * rendezvous cookie.

 */

int

rend_mid_establish_rendezvous(or_circuit_t *circ, const uint8_t *request,

                              size_t request_len)

{

  char hexid[9];

  int reason = END_CIRC_REASON_TORPROTOCOL;

  log_info(LD_REND, "Received an ESTABLISH_RENDEZVOUS request on circuit %u",

           (unsigned)circ->p_circ_id);

  if (circ->base_.purpose != CIRCUIT_PURPOSE_OR) {

    relay_increment_est_rend_action(EST_REND_UNSUITABLE_CIRCUIT);

    log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,

           "Tried to establish rendezvous on non-OR circuit with purpose %s",

           circuit_purpose_to_string(circ->base_.purpose));

    goto err;

  }

  /* Check if we are configured to defend ourselves from clients that

   * attempt to establish rendezvous points directly to us. */

  if (channel_is_client(circ->p_chan) &&

      dos_should_refuse_single_hop_client()) {

    relay_increment_est_rend_action(EST_REND_SINGLE_HOP);

    /* Note it down for the heartbeat log purposes. */

    dos_note_refuse_single_hop_client();

    /* Silent drop so the client has to time out before moving on. */

    return 0;

  }

  if (circ->base_.n_chan) {

    relay_increment_est_rend_action(EST_REND_UNSUITABLE_CIRCUIT);

    log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,

             "Tried to establish rendezvous on non-edge circuit");

    goto err;

  }

  /* A (pending) conflux leg must stay a plain OR circuit: changing its

   * purpose is treated as a close of the leg by the conflux subsystem. */

  if (circ->base_.conflux || circ->base_.conflux_pending_nonce) {

    relay_increment_est_rend_action(EST_REND_UNSUITABLE_CIRCUIT);

    log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,

           "Tried to establish rendezvous on a conflux circuit");

    goto err;

  }

  if (request_len != REND_COOKIE_LEN) {

    relay_increment_est_rend_action(EST_REND_MALFORMED);

    log_fn(LOG_PROTOCOL_WARN,

           LD_PROTOCOL, "Invalid length on ESTABLISH_RENDEZVOUS.");

    goto err;

  }

  if (hs_circuitmap_get_rend_circ_relay_side(request)) {

    relay_increment_est_rend_action(EST_REND_DUPLICATE_COOKIE);

    log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,

           "Duplicate rendezvous cookie in ESTABLISH_RENDEZVOUS.");

    goto err;

  }

  /* Acknowledge the request. */

  if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),

                                   RELAY_COMMAND_RENDEZVOUS_ESTABLISHED,

                                   "", 0, NULL)<0) {

    relay_increment_est_rend_action(EST_REND_CIRCUIT_DEAD);

    log_warn(LD_PROTOCOL, "Couldn't send RENDEZVOUS_ESTABLISHED cell.");

    /* Stop right now, the circuit has been closed. */

    return -1;

  }

  relay_increment_est_rend_action(EST_REND_SUCCESS);

  circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_REND_POINT_WAITING);

  hs_circuitmap_register_rend_circ_relay_side(circ, request);

  base16_encode(hexid,9,(char*)request,4);

  log_info(LD_REND,

           "Established rendezvous point on circuit %u for cookie %s",

           (unsigned)circ->p_circ_id, hexid);

  return 0;

 err:

  circuit_mark_for_close(TO_CIRCUIT(circ), reason);

  return -1;

}

/** Process a RENDEZVOUS1 cell by looking up the correct rendezvous

 * circuit by its relaying the cell's body in a RENDEZVOUS2 cell, and

 * connecting the two circuits.

 */

int

rend_mid_rendezvous(or_circuit_t *circ, const uint8_t *request,

                    size_t request_len)

{

  const or_options_t *options = get_options();

  or_circuit_t *rend_circ;

  char hexid[9];

  int reason = END_CIRC_REASON_INTERNAL;

  if (circ->base_.purpose != CIRCUIT_PURPOSE_OR || circ->base_.n_chan) {

    relay_increment_rend1_action(REND1_UNSUITABLE_CIRCUIT);

    log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,

           "Tried to complete rendezvous on non-OR or non-edge circuit %u.",

           (unsigned)circ->p_circ_id);

    reason = END_CIRC_REASON_TORPROTOCOL;

    goto err;

  }

  /* Same for a (pending) conflux leg: its purpose must not change. */

  if (circ->base_.conflux || circ->base_.conflux_pending_nonce) {

    relay_increment_rend1_action(REND1_UNSUITABLE_CIRCUIT);

    log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,

           "Tried to complete rendezvous on conflux circuit %u.",

           (unsigned)circ->p_circ_id);

    reason = END_CIRC_REASON_TORPROTOCOL;

    goto err;

  }

  if (request_len < REND_COOKIE_LEN) {

    relay_increment_rend1_action(REND1_MALFORMED);

    log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,

         "Rejecting RENDEZVOUS1 cell with bad length (%d) on circuit %u.",

         (int)request_len, (unsigned)circ->p_circ_id);

    reason = END_CIRC_REASON_TORPROTOCOL;

    goto err;

  }

  base16_encode(hexid, sizeof(hexid), (const char*)request, 4);

  log_info(LD_REND,

           "Got request for rendezvous from circuit %u to cookie %s.",

           (unsigned)circ->p_circ_id, hexid);

  rend_circ = hs_circuitmap_get_rend_circ_relay_side(request);

  if (!rend_circ) {

    /* Once this was a LOG_PROTOCOL_WARN, but it can happen naturally if a

     * client gives up on a rendezvous circuit after sending INTRODUCE1, but

     * before the onion service sends the RENDEZVOUS1 cell.

     */

    relay_increment_rend1_action(REND1_UNKNOWN_COOKIE);

    log_fn(LOG_DEBUG, LD_PROTOCOL,

         "Rejecting RENDEZVOUS1 cell with unrecognized rendezvous cookie %s.",

         hexid);

    reason = END_CIRC_REASON_TORPROTOCOL;

    goto err;

  }

  /* Statistics: Mark circuits as RP circuits */

  if (options->HiddenServiceStatistics) {

    /* `circ` is the RP <-> service circuit */

    circ->circuit_carries_hs_traffic_stats = 1;

    /* `rend_circ` is the client <-> RP circuit */

    rend_circ->circuit_carries_hs_traffic_stats = 1;

  }

  /* Send the RENDEZVOUS2 cell to the client. */

  if (relay_send_command_from_edge(0, TO_CIRCUIT(rend_circ),

                                   RELAY_COMMAND_RENDEZVOUS2,

                                   (char*)(request+REND_COOKIE_LEN),

                                   request_len-REND_COOKIE_LEN, NULL)) {

    relay_increment_rend1_action(REND1_CIRCUIT_DEAD);

    log_warn(LD_GENERAL,

             "Unable to send RENDEZVOUS2 cell to client on circuit %u.",

             (unsigned)rend_circ->p_circ_id);

    /* Stop right now, the circuit has been closed. */

    return -1;

  }

  relay_increment_rend1_action(REND1_SUCCESS);

  /* Join the circuits. */

  log_info(LD_REND,

           "Completing rendezvous: circuit %u joins circuit %u (cookie %s)",

           (unsigned)circ->p_circ_id, (unsigned)rend_circ->p_circ_id, hexid);

  circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_REND_ESTABLISHED);

  circuit_change_purpose(TO_CIRCUIT(rend_circ),

                         CIRCUIT_PURPOSE_REND_ESTABLISHED);

  hs_circuitmap_remove_circuit(TO_CIRCUIT(rend_circ));

  rend_circ->rend_splice = circ;

  circ->rend_splice = rend_circ;

  return 0;

 err:

  circuit_mark_for_close(TO_CIRCUIT(circ), reason);

  return -1;

}